Stents and similar devices such as stent, stent-grafts, expandable frameworks, and similar implantable medical devices, are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. Stents may be implanted in a variety of body lumens or vessels such as within the vascular system, urinary tracts, bile ducts, fallopian tubes, coronary vessels, secondary vessels, etc. Stents may be used to prevent restenosis following angioplasty in the vascular system. They may be self-expanding, expanded by an internal radial force, such as when mounted on a balloon, or a combination of self-expanding and balloon expandable (hybrid expandable).
A stent is typically an open tubular structure that has a pattern (or patterns) of apertures extending from the outer surface of the stent to the lumen. It is common to make stents of biocompatible metallic materials, with the patterns cut on the surface with a laser machine. The stent can be electro-polished to minimize surface irregularities since these irregularities can trigger or stimulate foreign body reactions or adverse biological responses such as thrombosis or restenosis.
Another way to further minimize such responses is by coating insertable and/or implantable medical devices with a variety of coating compositions including those comprising a biocompatible polymer. These coatings may also further incorporate therapeutic agents or biologically active materials. For example, implanted stents have been used to carry therapeutic agents such as thrombolytic agents.
See, for example, commonly assigned U.S. Pat. Nos. 6,885,770, 6,569,195, 6,358,556, 6,258,121, 6,120,847, 6,099,562, and 5,304,121 and U.S. Pat. Nos. 5,879,697 and 5,092,877, each of which is incorporated by reference herein in its entirety. See also commonly assigned 2004/0215169 which is incorporated by reference herein in its entirety.
Such coatings have been applied to the surface of a medical device by various methods, such as spray coating and dip coating. It can be difficult, when employing such conventional methods, for example, to coat only the outer surface without coating the inner surface of a tubular stent wall which has openings therein. Also, the ratio of coating thickness placed on the inner surface of the tubular wall and placed on the outer surface of the tubular wall created by a conventional method is fixed and cannot be varied. For example, when a dip coating method is employed, the thickness of the coating varies depending upon the geometry of the stent since the coating tends to collect where struts intersect and difficult to vary using such a method.
Furthermore, in some medical devices having a tubular wall, all of the surfaces of the medical device or portions thereof may not require coating, or may not require a coating which includes a biologically active material. For instance, the inner surface of a stent may not need a coating containing a biologically active material when the biologically active material is intended to be delivered to a body lumen wall, which only directly contacts the outer surface of the stent. The inner surface of the stent does not come in direct contact with the body lumen wall and does not apply the biologically active material to the body lumen wall. On the other hand, if the biologically active material is intended to be delivered to a body fluid rather than a body lumen wall, then the coating containing the biologically active material should be placed on the inner surface of the stent wall but is not needed on the outer surface.
In addition, it may be advantageous to apply different coatings on different portions of the tubular wall. For example, an expandable stent is often crimped into a reduced diameter state for delivery through a body lumen to the site of stent deployment. Therefore, it is advantageous that the coating on portions of the stent which contact each other in the stent's crimped state do not stick to one another which can result in damage to the coating. If the stent is balloon expandable and therefore crimped onto an expandable balloon member, the inner surface of the stent that contacts the balloon should not stick to the balloon during withdrawal of the balloon after the stent has been deployed. A lubricious outer surface facilitates smooth delivery through a body lumen.
There remains a need in the art for a method of coating a medical device comprising a tubular wall, such as a stent, which provides the ability to control placement of the coating on selected stent surfaces, such as the outer surface, but not the inner surface of the tubular wall.
The art referred to and/or described above is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.